Environmental Toxicology Environmental Health

What is Toxic? A characteristic of certain chemicals that are extremely stable and may take many years to be broken down into simpler forms by natural processes Synthetic chemicals (those not found in nature) Ex: DDT

Then what is Poison??

Important Concepts Bio-accumulation: The buildup of a persistent toxic substance in an organism’s body, often in fatty tissues Synthetic chemical do not metabolize well They remain in the body for extended periods of time Bio-magnification: The increased concentration of toxic chemicals in the tissues of organisms that are at higher levels in food webs

Continue Exposure: Any condition which provides an opportunity for an external environmental agent to enter the body Agent: Any chemical (cyanide), biological (venom), or physical material (radiation) capable of eliciting a biological response Difference between agent and vector??

Exposure Assessment Exposure = How much x How often x How long Exposure = Intensity x Frequency x Duration

Patterns of Exposure

What is Xenobiotic? Environmental xenobiotic are xenobiotic compounds with a biological activity that are found as pollutants in the natural environment Examples: Antibiotics, PCBs (Poly Chlorinated Biphenyls)

Endocrine Disruptors A chemical that mimics or interferes with the actions of the endocrine system in humans and wildlife i.e. It effects the ability of the hormones in the organisms to function properly Examples include: PCBs, Dioxins Heavy metals – lead and mercury DDT

Toxicology Toxicology is the study of the effect of toxicants on the human body Toxicant- chemical with adverse human health effects

Continue Acute toxicity Adverse effects occur within a short period after exposure to toxin Chronic toxicity Adverse effects occur some time after exposure, or after prolonged exposure to toxin Symptoms often mimic other diseases- hard to assess source

How to measure Toxicity? Toxicity measured by dose and response Dose: amount that enters that body of an exposed organism Response: the amount of damage caused by a specific dose LD50 A common dose estimate for acute toxicity Smaller the LD50, the more lethal the chemical Determined for all new synthetic chemicals

LD50 Lethal dose (LD50) is the amount of an ingested substance that kills 50 percent of a test sample. It is expressed in mg/kg, or milligrams of substance per kilogram of body weight Do you know about ED?

Dose-Response Curve Dose-Response Curve Illustrates the effect of different doses on a population Threshold Level Maximum dose with no measurable effects

Dose-Response Curve

Models Stochastic Model: Risk (probability) of response is a function of dose Assumes no threshold No dose is safe Any dose increases the risk Deterministic Model: A safe dose and a threshold exist

Does-Response Curve

Toxicology-Paradigms (Assignment) Dilution Paradigm: "the solution to pollution is dilution" Boomerang Paradigm: "what you throw away can come back and hurt you"

Continue Toxicologists should: Identify the mode / site of action of a xenobiotic FATE and TRANSPORT / interaction of a xenobiotic with the biosphere (including specific organisms) after it is released / pollution occurs

Identify the effect the xenoboitic has on an ecosystems Introduction of xenobiotic Ecosystem effect site of action biotransformation physiology behavior community parameters biochemistry population dynamics

Toxicology Paradigm

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Steps in reducing Lung Cancer Mortality

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